Aircraft are commonly equipped with one or more vision enhancing systems. Such vision enhancing systems are designed and configured to assist a pilot when flying in conditions that diminish the pilot's view from the cockpit, such as, but not limited to, darkness and weather phenomenon. One example of a vision enhancing system is known as a synthetic vision system (hereinafter, “SVS”). An example of a synthetic vision system is disclosed in U.S. Pat. No. 7,352,292 which is hereby incorporated herein by reference in its entirety. Additionally, an exemplary synthetic vision system is available for sale in the market place under product name SmartView, manufactured by Honeywell Inc.
A typical SVS is configured to work in conjunction with a position determining unit associated with the aircraft as well as dynamic sensors that sense the aircraft's altitude, heading, and orientation. The SVS includes a database containing information relating to the topography along the aircraft's flight path. The SVS receives inputs from the position determining unit indicative of the aircraft's location and also receives inputs from the dynamic sensors on board the aircraft indicative of the aircraft's heading, altitude, and orientation. The SVS is configured to utilize the position, heading, altitude, and orientation information and the topographical information contained in its database, and generate a three-dimensional image that shows the topographical environment through which the aircraft is flying from the perspective of a person sitting in the cockpit of the aircraft. The three-dimensional image may be displayed to the pilot on any suitable display unit accessible to the pilot. Using a SVS, the pilot can look at the display screen to gain an understanding of the three-dimensional topographical environment through which the aircraft is flying and can also see what lies ahead. One advantage of the SVS is that its image is clean and is not obstructed by any weather phenomenon. One drawback of the SVS is its dependence upon the information contained in the database. If the database is not up to date, then the image presented to the pilot may not be an accurate depiction of the topographical environment around the aircraft.
Another example of a vision enhancing system is known as an enhanced vision system (hereinafter, “EVS”). Examples of enhanced vision systems are disclosed in U.S. Pat. Nos. 7,655,908 and 5,317,394 which are hereby incorporated herein by reference in their entirety. Additionally, an exemplary enhanced vision system is available for sale in the market place under product name EVS-II, manufactured by Kollsman, Inc. A typical EVS includes an imaging device, such as, but not limited to, a visible lowlight television camera, an infrared camera, or any other suitable light detection system capable of detecting light or electromagnetic radiation, either within or outside of the visible light spectrum. Such imaging devices are mounted to the aircraft and oriented to detect light transmissions originating from an area outside of the aircraft and typically located ahead of the aircraft in the aircraft's flight path. The light received by the EVS is used by the EVS to form an image that is then displayed to the pilot on any suitable display in the cockpit of the aircraft. The sensor used in an EVS is more sensitive to light than is the human eye. Accordingly, using the EVS, a pilot can view elements of the topography that are not visible to the human eye. For this reason, an EVS is very helpful to a pilot when attempting to land an aircraft in inclement weather or at night. One advantage to an EVS system is that it depicts what is actually present versus depicting what is recorded in a database.
Some aircraft are equipped with both an EVS and an SVS. In such aircraft, the images from the EVS and the SVS are commonly shown to the pilot on the same display screen, with the image from the EVS (which is smaller than the image from the SVS) being overlaid on top of the image from the SVS such that the portion of the SVS image located below the EVS image may not be visible.
In addition to the above described vision systems, additional images, in the form of symbology, are typically presented to the pilot on the same display screen where the images from the EVS in the SVS are displayed. The symbology commonly appears as an icon or a series of icons on the display screen and may be indicative of the aircraft's heading, direction, attitude, and orientation. Such symbology serves an important role in providing the pilot with situational awareness and controls concerning the orientation and attitude of the aircraft. This symbology is traditionally overlaid over the image presented by the SVS and EVS.
The information provided by the EVS and the symbology play an important role in enabling the pilot to maintain situational awareness during the flight and in particular approach and landing during low visibility conditions, and neither can be dispensed with. During certain portions of the flight such as determining whether to proceed with a landing or to initiate a go-around procedure, the information provided by the EVS may have greater importance to the pilot than the information provided by the symbology. However, because the symbology is a relatively strong computer-generated image and because the EVS image is a relatively weak image compared to that of background, which is based on relatively weak light transmissions detected during lowlight or inclement weather conditions, the symbology may obscure, overpower, or blank out the EVS image or the critical signatures within an EVS image. Additionally, during other phases of the flight, the information provided by the SVS may be quite important to pilot and the overlaying of symbology over the SVS image may cause an undesirable amount of obscuring and cluttering of the SVS image.